Focusing on physical metallurgy and materials, Materials Week '97, which incorporates the TMS Fall Meeting, features a wide array of technical symposia sponsored by The Minerals, Metals & Materials Society (TMS) and ASM International. The meeting will be held September 14-18 in Indianapolis, Indiana. The following session will be held Wednesday afternoon, September 17.
THERMOMECHANICAL PROCESSING AND MECHANICAL PROPERTIES OF HYPEREUTECTOID STEELS AND CAST IRONS: Session II: Properties and Performance of Ultrahigh-Carbon Steels and Cast Irons
Sponsored by: SMD Structural Materials Committee
Program Organizers: Donald R. Lesuer, Chol K. Syn, Lawrence Livermore National Laboratory, P.O. Box 808, L-342, Livermore, CA 94550; Oleg D. Sherby, Stanford University, Dept. Materials Science & Eng., Stanford, CA 94305
Room: 212
Session Chair: George Mayer, ARO, Washington, D.C.; Bruce Bramfitt, Bethlehem Steel Corporation, Bethlehem, PA 19016
RAILROAD RAILS AND FROGS: APPLICATIONS FOR HYPEREUTECTOID STEELS: Roger K. Steele, Metallurgical Consulting Services Inc., Vernon, CT 06066
Currently, railroad rails and some switch frogs are manufactured from pearlitic eutectoid carbon steel. This steel can be hardened by on-line heat treatment in large tonnages to 400 BHN at little cost beyond that of basic rail. Although hypereutectoid steels can match the strength and ductility properties of the eutectoid steels (both pearlitic and bainitic), it is not clear that large quantities can be manufactured at high strength levels as economically as can the eutectoid steels. Also the issue of welding into very long rail strings is problematic. However, switch frogs which currently can utilize a cast austenitic manganese steel insert may be a potential application for hypereutectoid steels because no connective welding is necessary. The high impact and surface traction that can occur during wheel traversal of the flangeway gap has focused attention on high strength frog materials such as weld deposited maraging steels as well as low carbon, high strength bainitic steels The extraordinarily high strength coupled with modest ductility achievable with tempered martensitic hypereutectoid steels is attractive for this type of application.
1:50 pm
APPLICATION OF HYPEREUTECTOID STEEL FOR RAILS IN HEAVY HAUL TRACKS: Masaharu Ueda, Nippon Steel Corp., Kitakyushu-City, Japan
Currently, railroad rails and some switch frogs are manufactured from pearlitic eutectoid carbon steel. This steel can be hardened by on-line heat treatment in large tonnages to 400 BHN at little cost beyond that of basic rail. Although hypereutectoid steels can match the strength and ductility properties of the eutectoid steels (both pearlitic and bainitic), it is not clear that large quantities can be manufactured at high strength levels as economically as can the eutectoid steels. Also the issue of welding into very long rail strings is problematic. However, switch frogs which currently can utilize a cast austenitic manganese steel insert may be a potential application for hypereutectoid steels because no connective welding is necessary. The high impact and surface traction that can occur during wheel traversal of the flangeway gap has focused attention on high strength frog materials such as weld deposited maraging steels as well as low carbon, high strength bainitic steels The extraordinarily high strength coupled with modest ductility achievable with tempered martensitic hypereutectoid steels is attractive for this type of application.
2:10 pm
MECHANICAL BEHAVIOR OF ULTRAHIGH STRENGTH, ULTRAHIGH-CARBON STEEL WIRE AND ROD: Donald R. Lesuer, Chol K. Syn, Lawrence Livermore National Laboratory, P.O. Box 808, L-342, Livermore, CA 94550; Oleg D. Sherby, Stanford University, Dept. Materials Science & Eng., Stanford, CA 94305
Ultrahigh-carbon steels (UHCSs) can achieve very high strengths in wire or rod form. These high strengths result from the mechanical work introduced during wire and rod processing. These strengths have been observed to increase in a linear manner with carbon content. In wire form, tensile strengths greater than 5000 MPa are predicted for UHCS containing 1.8%C. In this presentation we will discuss the influence of processing (including rapid transformation processes used during wire patenting) and microstructure on the mechanical behavior of UHCS wire. The tensile properties of as-extruded rods are described as a function of extrusion temperature and composition. For spheroidized steels, yield and ultimate strength are a function of grain size, interparticle spacing and particle size. For pearlitic steels, yield and ultimate strength were found to be functions of colony size, carbide size and plate spacing and orientation. Alloying additions (such as C, Cr, Si, Al and Co) can influence the effect of processing on these microstructural features. For both spheroidized and pearlitic steels, fracture was found to be a function of carbide size and composition.
2:30 pm
MECHANICAL BEHAVIOR OF A HYPEREUTECTOID STEEL EXHIBITING A DAMASK SURFACE PATTERN: Eric M. Taleff1, Chol K. Syn2, Donald R. Lesuer2, Oleg D. Sherby3, 1The University of Texas at Austin, Austin, Texas, 2Lawrence Livermore National Laboratory, Livermore, CA; 3Stanford Univ., Stanford, CA; D.K. Kim, The Goodyear Tire & Rubber Co., Akron Ohio 44309; W. Daniel Whittenberger, NASA-Lewis Research Center, Cleveland OH 44135
Hypereutectoid steel plates have been produced by industrial processing methods, including hot and warm rolling, to exhibit a surface Damask marking. This marking is similar to those exhibited by the famous Damascus Steels, which were also of hypereutectoid composition. The microstructure of this material contains fine spheroidized carbides and a discontinuous carbide network along former austenite grain boundaries, which give rise to the Damask pattern. Tension tests conducted at room temperature reveal tensile strengths of up to 1,100 MPa and tensile ductilities beyond 8% in this modern Damascus Steel. The rolling process used to produce the plate material results in a slight directionality in strength and ductility.
2:50 pm
MECHANICAL PROPERTIES AND STRUCTURAL SUPERPLASTICITY IN ULTRAHIGH- CARBON STEELS AND BORON ALLOY TOOL STEELS PRODUCED BY RAPID SOLIDIFICATION AND POWDER METALLURGY: G. Frommeyer, U. Giegel, H.J. Speis, J.A. Jimenez, Max Planck Institut fur Eisenforschung GmbH, Dusseldorf, Germany
Ultrahigh carbon and boron tool steels with fine grained microstructures consisting of equiaxed 
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-matrix grains (3 to 5 µm in size) and a fine dispersion of special carbides or borides (1 to 3 µm in size) were prepared by rapid solidification technology - argon melt atomization - and consolidated by extrusion or hot isostatic pressing. These steels exhibit structural superplasticity in the temperature regime from 800 to 1050°C depending upon their composition. The paper presents the mechanical properties and structural superplasticity of selected ultrahigh carbon alloy tool steels with carbon contents up to 2.5 mass%, 8-10 mass% vanadium, 5-10 mass% chromium and molybdenum, and ultrahigh boron alloy steels with boron contents up to 2.5 mass%, 25 mass% chromium, and 10 mass% nickel. The superior strength properties, wear and corrosion resistance favor these steels to be used for a large variety of applications. The superplastic properties enable near net shape forming of cutting tools, dies etc. with complex geometry.
3:10 pm BREAK
3:30 pm
TENSILE ELONGATION BEHAVIOR OF FINE-GRAINED Fe-C ALLOYS AT ELEVATED TEMPERATURE: Woo-Jin Kim, Hong-Ik University, Seoul, 121-791, Korea
Tensile elongation behavior of fine-grained Fe-C alloys has been investigated as a function of cementite volume fraction, degree of microstructural refinement, and the Zener-Hollomon parameter. The strain rate-stress relationships and creep strengths of Fe-C alloys with carbon contents from 1.3 to 5.25wt.%C are found to be similar when grain size is similar. Room-temperature strength, however, is found to be a function of the volume percent of cementite. Superplastic ductility of ingot-processed alloys increases with carbon content (cementite volume fraction) but starts to decrease after 2.1%C. The increase of tensile ductility from 1.3 to 2.1%C is attributed to reduction of dynamic grain growth rate with increase of fine cementite particles with carbon contents, whereas the decrease of tensile ductility above 2.1%C is due to the increase in number of coarse cementite particles and to an increase in the area of cementite/cementite grain boundaries. Superplastic ductility of Fe-C alloys with carbon contents higher than 2.1%C can be significantly enhanced when powder-processing routes are utilized instead of ingot-processing routes. Tensile elongation behavior of cementite-based alloys is revealed to be different from that of iron-based alloys when compared as a function of the Zener-Hollomon parameter.
3:50 pm
PROCESSING AND SUPERPLASTICITY OF STAINLESS STEEL CLAD ULTRAHIGH CARBON STEEL: Glenn S. Daehn1, Oleg D. Sherby, Stanford University, Dept. Materials Science & Eng., Stanford, CA 94305; 1The Ohio State University, Dept. of Materials Science & Eng., 116 W. 19th Ave., Columbus, OH 43210-1179
Lamination of a non-superplastic material to a superplastic one can result in a composite that behaves superplastically if the majority of the composite strength resides in the superplastic material. This concept is used in the specific case of laminating ferritic stainless steel to an ultrafine grained ultrahigh carbon steel to produce composites that can be superplastically formed at temperatures near 775°C. In this work we have developed processing routes that can: provide ultrafine grained structures in the ultrahigh carbon steel, give effective lamination, include diffusion barriers and result in composites that have been superplastically formed. It appears that with modest development this concept could be used to build large high-strength, stainless-clad structures.
4:10 pm
HYPEREUTECTOID STEELS AND CAST IRONS: Hong Li, University of Michigan, Ann Arbor, MI 48109
The research is concerned with the study of structural refinement and superplasticity in hypo-eutectic low alloy white cast irons. Three white cast irons, containing 2.2, 2.6 and 3.0%C were investigated. in order to obtain a fine grained structure, thermomechanical processing methods were used. The mechanism of carbide refinement occurring during both hot working and warm working were analyzed using optical, scanning electron and transmission electron microscopy. Mechanical tests both in tension and in compression for fine grained cast irons were performed at elevated temperatures. It was concluded that white cast iron ingots containing up to 3.0%C are capable of undergoing extensive hot forging, hot rolling and warm rolling in the range from 700°C to 1000°C. Thermomechanical processing produced a fine grained superplastic structure in cast irons. The fine-grained cast irons exhibit good superplasticity and high strain rate sensitivity in both tension and compression in the temperature range of 650-770°C. Tensile elongation to failure of 220%, 150% and 80% were obtained for 2.2%C, 2.6%C and 3.0%C cast irons, respectively.
4:30 pm
ULTRAHIGH CARBON STEEL AND DUCTILE IRON RESEARCH IN SPAIN: O.A. Ruano1, M. Carsi1, C. Bertrand2, J. Ibanez1, F. Penalba3, O.D. Sherby4, 1Centro Nacional de Investigaciones Metalurgicas, Madrid, Spain; 2SIDENOR I+D, Vizcaya, Spain; 3INASMET, San Sebastian, Spain; 4Stanford University, Stanford, CA
Ultrahigh carbon steel (UHCS) and ductile iron research and development work is reported on studies at three different research and development laboratories in Spain. Emphasis has been placed on studies of the ductility and strength at high strain rates and high temperatures by means of torsion testing. These studies are to simulate the processing steps in the manufacture of contemporary steels. It is shown that UHCS is slightly weaker and as ductile as low carbon steels at high strain rates (10 to 26 s-1) in the range of 1000 to 1200°C. The conditions under which the deleterious proeutectoid carbide network in UHCS can be avoided has been assessed. Fast cooling after hot working leads to a pearlitic structure and the room temperature hardness of pearlite is shown to be principally a function of the temperature of working and secondarily of the dilute alloy additions. Spot welding studies of a 1.5%C steel sheet have been made. A strength of 725 MPa was obtained for the welded sample after annealing at 800°C for 5 minutes and furnace cooling. Ductile iron research has lead to development of austempered ductile iron with a structure consisting of fine bainite with nodular graphite. Ultimate tensile strengths over 800 MPa with elongations to failure of over 10% elongation were obtained.
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